1. Field of the Invention
The present invention relates to a magnetic disk drive provided with a load-unload mechanism, in which the reliability of the drive is ensured when part of a suspension impinges on a ramp during an unloading operation. The present invention is suitably applied to a small-size magnetic disk apparatus employing magnetic disks of a small size such as 3.5 inch, 3 inch, 2.5 inch, 1.8 inch, 1.3 inch, 1 inch and 0.7 inch.
2. Related Art
A conventional small-size magnetic disk apparatus will be described with taking a small size magnetic disk apparatus disclosed in JP-A-6-96532 as an example. Information-recording magnetic disks, arranged in a stacked manner, are rotated at a constant speed by a spindle motor fixedly mounted on a base. A head, mounted on a slider, is supported on a carriage through a suspension, and flies with a minute distance above the disk so as to record and reproduce information. The high-speed, high-precision positioning of the head is effected by rotating (pivotally moving) the carriage by a voice coil motor. A pivot assembly, comprising a sleeve in which a pivot shaft and two ball bearings are received, is mounted on the carriage, and the pivot assembly is fixed on the base, so that the carriage can be rotated about the pivot shaft. The voice coil motor for driving the carriage comprises a driving coil, permanent magnets and a yoke. The driving coil is mounted on the carriage whereas the remaining elements, that is, the permanent magnets and the yoke (which will be hereinafter referred as xe2x80x9cmagnet-yoke assemblyxe2x80x9d), are fixedly secured on the base. The driving coil, interposed between magnetic circuits, is subjected to the magnetic field action, and therefore by energizing the driving coil, the carriage can be driven, so that the head can be located at a desired position of the disk.
In a small-size disk apparatus, to enhance the recording density and an impact resistance is most important. To achieve this, there has been proposed a device equipped with a load-unload mechanism. The mainstream of such mechanism system is called xe2x80x9cramp loadxe2x80x9d, and is disclosed, for example, in U.S. Pat. Nos. 5,237,472 and 5,574,604. A lift-tab, projected from a distal end of a suspension, is driven while guided by a curved cam surface (which is called a ramp), thereby loading the head onto the disk. When the read/write operation is finished, the head is unloaded from the disk, and is evacuated to the ramp. In this system, the head is evacuated from the disk, and therefore there is no fear of head-stiction. Therefore, there is no need to apply a conventional head-stiction prevention processing, such as texturing, to the disk, and a smooth disk can be used. Therefore, the flying height of the head can be reduced, and the recording density can be enhanced. And besides, since the head is evacuated from the disk, the impact resistance in an inoperative condition can be markedly enhanced.
Prior art techniques, which are liable to be confused with the present invention, are disclosed in JP-A-08-129840 and JP-A-08-161842. More specifically, these publications disclose a disk apparatus in which in order to increase a recording range of a magnetic disk, the position of a ramp in a disk rotation stand-by condition (during the loading operation or during the unloading operation) is different from the position of the ramp during the rotation of the disk (during the recording or during the reproducing). However, in these publications, there is no mention of the type of disk apparatus in which the ramp is so supported that the position of the ramp can be displaced during the loading and unloading operations.
In the ramp load system, disclosed in any of the above patents, the lift-tab, projected from the distal end of the suspension, is fixedly secured to the suspension, and the ramp is fixedly mounted on the base by screws or the like. Therefore, an impact force, produced by impingement occurring when the lift-tab slides onto the ramp during the unloading operation, is excessive, and can damage the head. And besides, as a result of this impingement, the lift-tab and the head are worn, and wear debris, resulting from these worn parts, deposits on the disk, the slider, the head and so on, and in some cases, this causes an operation failure or malfunction. Therefore, the number of loading and unloading operations has been limited.
It is an object of the present invention to provide a magnetic disk apparatus provided with a load-unload mechanism of high reliability, in which even if loading and unloading operations are frequently repeated, damage to a head due to impingement of a lift-tab during the unloading operation is eliminated, and the lift-tab and a ramp are less liable to wear, and an operation failure or malfunction due to wear debris is eliminated.
According to the present invention, there is provided a magnetic disk apparatus comprising a ramp serving as a guide for loading a head onto a disk and for unloading the head from the disk, wherein part of a suspension slides over the ramp so as to effect the loading operation and the unloading operation, and the ramp is so supported that during each of the loading and unloading operations, the position of the ramp can be displaced. In other words, during the loading operation, the position or the posture of the ramp is changed when the lift-tab begins to slide over the ramp. During the unloading operation, the position or the posture of the ramp is changed immediately after the lift-tab impinges on the ramp.
Further, in the present invention, the position or the posture of the ramp may be changed during the unloading operation.
In the present invention, one or two restraining members for restraining the position or the posture of the ramp are mounted on a base or a cover. When part of the suspension slides over the ramp during the loading operation or during the unloading operation, a friction force acts on the ramp, and the ramp is displaced until the ramp strikes against the restraining member, so that the position or posture of the ramp during the loading operation is different from the position or the posture of the ramp during the unloading operation.
In the present invention, a cushioning member, made of an elastic material or a viscous-elastic material, is provided on one of those portions of the ramp and the restraining member for contact with each other.
In the present invention, the ramp is supported for rotational displacement.
In the present invention, the ramp is supported for translational movement.
In the present invention, the restraining member is made of an elastic material or a viscous-elastic material.